Electrical circuit, thin film transistor, method for manufacturing electric circuit and method for manufacturing thin film transistor

ABSTRACT

An electrical circuit containing a substrate having thereon a receptive layer, wherein the receptive layer has a conductive polymer impregnated in the receptive layer, and a method for forming the electrical circuit.

This application is a U.S. National Phase Application under 35 USC 371of International Application PCT/JP2003/012140 filed Sep. 24, 2003.

TECHNICAL FIELD

The present invention relates to an electrical circuit and a productionmethod of the same, as well as a thin film transistor and a productionmethod of the same.

BACKGROUND OF THE INVENTION

Common methods for forming electrical circuit patterns on a substrateare such that after forming, on the entire surface of the substrate, aconductive film, an insulating film, a semiconductor film, and adielectric film, employing vacuum processes such as sputtering, circuitpatterning is performed employing photolithographic techniques.Photolithographic techniques, as described herein, refer to the methodin which a photosensitive resist is applied onto the thin film to besubjected to patterning, and after being exposed via a photomask anddeveloped, thin exposed film portions are subjected to dry etching orwet etching. Thereafter, commonly, the resist is peeled off and afterforming a film of another material, the photolithographic process isrepeated.

Recently, a method for directly forming a pattern without using aphotolithographic method but using an ink-jet printing head has beentested. In this method, an ink containing a desired material for theelectrical circuit is employed. By using such a method, it has becomepossible to simplify formation of circuit patterns.

In the above example of employing an ink-jet head, ejected ink spreadsover a substrate, which prevents formation of highly resolutionalpatterns. Namely, it has been difficult to uniformly place an ink at adesired position on the substrate.

As a technique to overcome the problem in which the ink spreads over asubstrate, for example, Japanese Patent Publication Open to PublicInspection (hereafter referred to as JP-A) No. 11-274681 discloses atechnique in which an adsorbing layer for the solvent of the ink isprovided on the substrate.

However, the above technique also has a problem in that the solute ofthe ink is not impregnated in the adsorbing layer resulting in formingan accumulation of patterning materials on the surface of the adsorbinglayer, which is not suitable for manufacturing a complicated circuitpattern, for example, a three-dimensional circuit pattern.

Further, heretofore, in order to protect the accumulated ink solutes onthe surface of the adsorbing layer, a protective layer has beenprovided. However, this method not only increases the number of worksteps but also makes it difficult to use a polymer support which issuitably used for a flexible print circuit, as well as a flexibledisplay.

Still further, WO 01/47043 discloses a technique in which by patternformation via ejecting ink of an aqueous dispersion of conductivepolymers, a source electrode and a drain electrode are formed, whereby atop gate type thin organic film transistor (an organic TFT) is prepared.

However, in this method, there have been a disadvantage that it takestime until the solution is dried and pattern formation is completed. Inaddition, patterning accuracy degrades due to spreading of liquiddroplets. Further, since a polyimide film is employed to form a channelvia photolithography, complicated process are required, resulting infurther increase in the production cost.

SUMMARY OF THE INVENTION

In view of the foregoing problems, the present invention was achieved.An object of the present invention is to provide an electrical circuitas well as a thin film transistor capable of being simply and quicklyformed without a thermal treatment, a method for simply and quicklyforming an electrical circuit having a fine and complex circuit pattern,and a method for producing a thin film transistor.

The object of the present invention is achieved by the followingstructures.

-   (1) An electrical circuit containing a substrate having thereon a    receptive layer, wherein the receptive layer has a conductive    polymer impregnated in the receptive layer.-   (2) The electrical circuit of claim (1), further containing a    terminal made of an electrical conductor or a semiconductor on the    substrate, the receptive layer being adjacent to the terminal,    whereby the conductive polymer is electrically connected with the    terminal so as to form at least a part of the electrical circuit.-   (3) The electrical circuit of Item (1) or Item (2),

wherein:

the conductive polymer is an oligomer having a repeat number of 4 to 19or a polymer having a repeat number of 20 or more; and

the conductive polymer has a repeat unit of thiophene, vinylene,thienylene vinylene, phenylene vinylene, p-phenylene or substituentcompounds thereof.

-   (4) The electrical circuit of Item (3), wherein the conductive    polymer is an oligomer or a polymer having thiophene or substituted    thiophene as the repeat unit.-   (5) The electrical circuit of Item (3) or Item (4), wherein the    oligomer or the polymer contains a dopant.-   (6) The electrical circuit of any one of Items (1) to (5), wherein    an electrical conductivity of the conductive polymer is 0.01 S/cm or    more.-   (7) The electrical circuit of Item (6), wherein the electrical    conductivity of the conductive polymer is 1 S/cm or more.-   (8) The electrical circuit of any one of Items (1) to (7), wherein    the receptive layer is porous.-   (9) The electrical circuit of Item (8), wherein the receptive layer    contains inorganic particles.-   (10) The electrical circuit of Item (9), wherein the inorganic    particles are fumed silica particles.-   (11) The electrical circuit of Item (9) or Item (10), wherein an    average particle diameter of the inorganic particles is 0.003 to 0.2    μm.-   (12) The electrical circuit of Item (11), wherein the average    particle diameter of the inorganic particles is 0.005 to 0.1 μm.-   (13) The electrical circuit of-any one of Items (9) to (12),    wherein:

the receptive layer further contains a hydrophilic binder; and

a weight ratio of the inorganic particles to the hydrophilic binder isbetween 2:1 and 20:1.

-   (14) The electrical circuit of any one of Items (1) to (13), wherein    the substrate is a polymer.-   (15) A thin film transistor containing a substrate having thereon:

a semiconductor layer;

a receptive layer adjacent to the semiconductor layer;

a gate electrode; and

a gate insulator layer provided:

-   -   between the receptive layer and the gate electrode; and    -   between the semiconductor layer and the gate electrode,

wherein the receptive layer comprises:

a source electrode made of a conductive polymer impregnated in thereceptive layer; and

a drain electrode made of the conductive polymer impregnated in thereceptive layer,

the source electrode and the drain electrode each being in contact withthe semiconductor layer.

-   (16) The thin film transistor of Item (15),

wherein:

the conductive polymer is an oligomer having a repeat number of 4 to 19or a polymer having a repeat number of 20 or more; and

the conductive polymer has a repeat unit of thiophene, vinylene,thienylene vinylene, phenylene vinylene, p-phenylene or substituentcompounds thereof.

-   (17) The thin film transistor of Item (16), wherein the conductive    polymer is an oligomer or a polymer having thiophene or substituted    thiophene as a repeat unit.-   (18) The thin film transistor of any one of Items (16) to (17),    wherein the oligomer or the polymer contains a dopant.-   (19) The thin film transistor of claim 16, wherein an electrical    conductivity of the conductive polymer is 0.01 S/cm or more.-   (20) The thin film transistor of Item (19), wherein the electrical    conductivity of the conductive polymer is 1 S/cm or more.-   (21) The thin film transistor of any one of Items (15) to (20),    wherein the receptive layer is porous.-   (22) The thin film transistor of Item (21), wherein the receptive    layer contains inorganic particles.-   (23) The thin film transistor of Item (22), wherein the inorganic    particles are fumed silica particles.-   (24) The thin film transistor of Item (22) or Item (23), wherein an    average particle diameter of the inorganic particles is 0.003 to 0.2    μm.-   (25) The thin film transistor of Item (24), wherein the average    particle diameter of the inorganic particles is 0.005 to 0.1 μm.-   (26) The thin film transistor of Item (22) or Item (25), wherein:

the receptive layer further contains a hydrophilic binder; and

a weight ratio of the inorganic particles to the hydrophilic binder isbetween 2:1 and 20:1.

-   (27) The electrical circuit of Item (15) or Item (26), wherein the    substrate is a polymer.-   (28) A method for manufacturing an electrical circuit containing a    step of forming at least a part of the circuit by impregnating a    conductive polymer in a receptive layer.-   (29) The method for manufacturing the part of the electrical circuit    of Item (28), containing the steps of:

impregnating a solution or a dispersed liquid containing the conductivepolymer in the receptive layer; and

forming the part of the electrical circuit by evaporating a solvent of asolution containing the conductive polymer or a dispersant of adispersed liquid containing the conductive polymer.

-   (30) The method for manufacturing the electrical circuit of Item    (29), wherein the solvent of the solution containing the conductive    polymer or the dispersant of the dispersed liquid containing the    conductive polymer contains 30% or more of water.-   (31) The method for manufacturing the electrical circuit of Item    (29), wherein the solvent of the solution containing the conductive    polymer or the dispersant of the dispersed liquid containing the    conductive polymer contains 5 to 70% by weight of a water soluble    organic solvent.-   (32) The method for manufacturing the electrical circuit of Item    (31), wherein the solvent of the solution containing the conductive    polymer or the dispersant of the dispersed liquid containing the    conductive polymer contains 10 to 30% by weight of a water soluble    organic solvent.-   (33) The method for manufacturing the electrical circuit of Item    (29), wherein the solution or the dispersed liquid containing the    conductive polymer has 0.001 to 1% by weight of a surfactant.-   (34) The method for manufacturing the electrical circuit of Item    (33), wherein the surfactant is a nonion surfactant.-   (35) The method for manufacturing the electrical circuit of Item    (28), wherein the part of the electrical circuit is formed by    ejecting the conductive polymer onto the receptive layer by a    ink-jet printing method so as to impregnate the ejected conductive    polymer in the receptive layer.-   (36) The method for manufacturing the electrical circuit of Item    (29), wherein the solution or the dispersed liquid containing the    conductive polymer is impregnated in the receptive layer by ejecting    the solution or the dispersed liquid containing the conductive    polymer onto the receptive layer by a ink-jet printing method.-   (37) The method for manufacturing the electrical circuit of Item    (28), wherein an amount of the conductive polymer impregnated in the    receptive layer is controlled by controlling an amount of the    ejected conductive polymer per unit area.-   (38). The method for manufacturing the electrical circuit of Item    (29), wherein an amount of the conductive polymer impregnated in the    receptive layer is controlled by controlling an amount of the    ejected solution or the dispersed liquid containing the conductive    polymer per unit area.-   (39) The method for manufacturing the electrical circuit of any one    of Items (28) to (38),

wherein:

the conductive polymer is an oligomer having a repeat number of 4 to 19or a polymer having a repeat number of 20 or more; and

the conductive polymer has a repeat unit of thiophene, vinylene,thienylene vinylene, phenylene vinylene, p-phenylene or a substituentcompound thereof.

-   (40) The method for manufacturing the electrical circuit of Item    (39), wherein the conductive polymer is an oligomer or a polymer    having thiophene or substituted thiophene as a repeat unit.-   (41) The method for manufacturing the electrical circuit of    Item (39) or Item (40), wherein the oligomer or the polymer contains    a dopant.-   (42) The method for manufacturing the electrical circuit of any one    of Items (28) to (41), wherein an electrical conductivity of the    conductive polymer is 0.01 S/cm or more.-   (43) The method for manufacturing the electrical circuit of Item    (42), wherein the electrical conductivity of the conductive polymer    is 1 S/cm or more.-   (44) The method for manufacturing the electrical circuit of any one    of Items (28) to (43), wherein the receptive layer is porous.-   (45) The method for manufacturing the electrical circuit of Item    (44), wherein the receptive layer contains inorganic particles.-   (46) The method for manufacturing the electrical circuit of Item    (45), wherein the inorganic particles are fumed silica particles.-   (47) The method for manufacturing the electrical circuit of    Item (45) or Item (46), wherein an average particle diameter of the    inorganic particles is 0.003 to 0.2 μm.-   (48) The method for manufacturing the electrical circuit of Item    (47), wherein the average particle diameter of the inorganic    particles is 0.005 to 0.1 μm.-   (49) The method for manufacturing the electrical circuit of any one    of Items (43) to (48), wherein:

the receptive layer further contains a hydrophilic binder; and

a weight ratio of the inorganic particles to the hydrophilic binder isbetween 2:1 and 20:1.

-   (50) The method for manufacturing the electrical circuit of any one    of Items (28) to (49), wherein the substrate is a polymer.-   (51) A method for manufacturing a thin film transistor containing    the steps of:

forming a semiconductor layer on a substrate;

forming a receptive layer adjacent to the semiconductor layer;

forming a source electrode in the receptive layer being in contact withthe semiconductor layer by impregnating a conductive polymer in thereceptive layer;

forming a drain electrode in the receptive layer being in contact withthe semiconductor layer by impregnating the conductive polymer in thereceptive layer;

forming a gate electrode; and

forming a gate insurator layer:

-   -   between the semiconductor layer and the gate electrode; and    -   between the receptive layer and the gate electrode.

-   (52) The method for manufacturing the thin film transistor of Item    (51), containing the steps of:

impregnating a solution or a dispersed liquid containing the conductivepolymer in the receptive layer; and

forming the source electrode and the drain electrode by evaporating asolvent of the solution containing the conductive polymer or adispersant of the dispersed liquid containing the conductive polymer.

-   (53) The method for manufacturing the thin film transistor of Item    (52), wherein the solvent of the solution containing the conductive    polymer or the dispersant of the dispersed liquid containing the    conductive polymer contains 30% or more of water.-   (54) The method for manufacturing the thin film transistor of Item    (52), wherein the solvent of the solution containing the conductive    polymer or the dispersant of the dispersed liquid containing the    conductive polymer contains 5 to 70% by weight of a water soluble    organic solvent.-   (55) The method for manufacturing the thin film transistor of Item    (54), wherein the solvent of the solution containing the conductive    polymer or the dispersant of the dispersed liquid containing the    conductive polymer contains 10 to 30% by weight of a water soluble    organic solvent.-   (56) The method for manufacturing the thin film transistor of Item    (52), wherein the solution or the dispersed liquid containing the    conductive polymer contains 0.001 to 1% by weight of a surfactant.-   (57) The method for manufacturing the thin film transistor of Item    (56), wherein the surfactant is a nonion surfactant.-   (58) The method for manufacturing the thin film transistor of Item    (51), wherein the source electrode and the drain electrode are    formed by ejecting the conductive polymer onto the receptive layer    by a ink-jet printing method so as to impregnate the ejected    conductive polymer in the receptive layer.-   (59) The method for manufacturing the thin film transistor of Item    (52), wherein the solution or the dispersed liquid containing the    conductive polymer is impregnated in the receptive layer by ejecting    the solution or the dispersed liquid containing the conductive    polymer onto the receptive layer by a ink-jet printing method.-   (60) The method for manufacturing the thin film transistor of Item    (58), wherein an amount of the conductive polymer impregnated in the    receptive layer is controlled by controlling an amount of the    ejected conductive polymer per unit area.-   (61) The method for manufacturing the thin film transistor of Item    (59), wherein an amount of the conductive polymer impregnated in the    receptive layer is controlled by controlling an amount of the    ejected solution or the dispersed liquid containing the conductive    polymer per unit area.-   (62) The method for manufacturing the thin film transistor of any    one of Items (51) to (61),

wherein:

the conductive polymer is an oligomer of which a repeat number is 4 to19 or a polymer of which a repeat number is 20 or more; and

the conductive polymer has a repeat unit of thiophene, vinylene,thienylene vinylene, phenylene vinylene, p-phenylene or substituentcompounds thereof.

-   (63) The method for manufacturing the thin film transistor of Item    (62), wherein the conductive polymer is an oligomer or a polymer    having thiophene or substituted thiophene as a repeat unit.-   (64) The method for manufacturing the thin film transistor of    Item (62) or Item (63), wherein the oligomer or the polymer contains    a dopant.-   (65) The method for manufacturing the thin film transistor of any    one of Items (51) to (64), wherein an electrical conductivity of the    conductive polymer is 0.01 S/cm or more.-   (66) The method for manufacturing the thin film transistor of Item    (65), wherein the electrical conductivity of the conductive polymer    is 1 S/cm or more.-   (67) The method for manufacturing the thin film transistor of any    one of Items (51) to (66), wherein the receptive layer is porous.-   (68) The method for manufacturing the thin film transistor of Item    (67), wherein the receptive layer contains inorganic particles.-   (69) The method for manufacturing the thin film transistor of Item    (68), wherein the inorganic particles are fumed silica particles.-   (70) The method for manufacturing the thin film transistor of    Item (68) or Item (69), wherein an average particle diameter of the    inorganic particles is 0.003 to 0.2 μm.-   (71) The method for manufacturing the thin film transistor of Item    (70), wherein the average particle diameter of the inorganic    particles is 0.005 to 0.1 μm.-   (72) The method for manufacturing the thin film transistor of any    one of Items (64) to (71), wherein:

the receptive layer further contains a hydrophilic binder; and

a weight ratio of the inorganic particles to the hydrophilic binder isbetween 2:1 and 20:1.

-   (73) The method for manufacturing the thin film transistor of any    one of Items (51) to (72), wherein the substrate is a polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing one example of the electrical circuitof the present invention.

FIG. 2( a) to FIG. 2( c) illustrate one example of the productionprocess of the electrical circuit of the present invention.

FIG. 2( d) is a plan view showing part of the electrical circuit of thepresent invention.

FIG. 3( a) is a sectional view of one example of the thin filmtransistor of the present invention.

FIG. 3( b) is a plan view of one example of the thin film transistor ofthe present invention.

FIG. 4( a) to FIG. 4( e) illustrate one example of the productionprocess of the thin film transistor of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention will now be detailed withreference to the drawings, but the present invention is not limitedthereto. Further, in the following description, some of the terms areused to refer to specific meanings. Such cases show preferred examplesof the present invention, and neither the meaning of the terms nor thetechnical range of the present invention is limited thereto.Incidentally, in the description of the figures, description fornumerals which are the same as those used in FIG. 1 and FIGS. 2( a)-2(d)are occasionally omitted. However, numerals refer to the samedescription used in FIG. 1 and FIGS. 2( a)-2(d), unless otherwisespecified.

FIG. 1 is a sectional view of one example of the eclectic circuit of thepresent invention.

In FIG. 1, numeral 1 is a substrate, while 2 is a receptive layer.Numeral 3 is a circuit pattern which is formed by impregnatingconductive polymers into receptive layer 2. Numeral 4 is a terminal, andfor example, when an electrical circuit is a thin film transistor,refers to a source bus line, a display electrode, or a semiconductor.

The electrical circuit of FIG. 1 incorporates receptive layer 2 onsubstrate 1, and circuit pattern 3 is formed by impregnating conductivepolymers into the above receptive layer However, in the electricalcircuit of the present invention, not all the circuit patterns may beformed with conductive polymers provided that at least some part of themis formed by impregnating conductive polymers into receptive layer 2 toform circuit pattern 3. Since the conductive polymer is not accumulatedon the surface of receptive layer 2, but is impregnated and fixed withinreceptive layer 2, undesirable spread of conductive polymers issuppressed, whereby it is possible to form detailed circuit pattern 3.

Further, even though the surface of receptive layer 2 may suffer fromdamage due to accidental scratches, it is possible to minimize thedamage due to the fact that circuit pattern 3 is impregnated into thereceptive layer. Consequently, differing from the conventionaltechnique, it is unnecessary to provide a protective film on the surfaceof the receptive layer. Further, since durability is enhanced byproviding receptive layer 2, a heat treatment process such as annealingis not necessary. Accordingly, it is possible to quickly and simplyproduce electrical circuits.

Still further, in the electrical circuit of the present invention,electrical circuit pattern 3 is formed by impregnating conductivepolymers into receptive layer 2, whereby it is possible to form complexcircuit patterns. For example, as shown in FIGS. 2( a)-2(c) of theproduction process of the electrical circuit, as well as in FIG. 2( d)of the plan view of the electrical circuit, circuit pattern 3 is formedin receptive layer 2 (FIG. 2( a)), and receptive layer 2′ is providedthereon (FIG. 2( b)). Further, new circuit pattern 3′ is formed onreceptive layer 2′. By combining circuit pattern 3 with circuit pattern3′ (FIG. 2( c)), it becomes possible to form more complex circuitpatterns 3, 3′ (FIG. 2( d)).

The present invention will now be described in more detail.

π conjugated oligomers and π conjugated polymers are preferably employedas a conductive polymer of the present invention. Examples of usablecompounds include polypyrroles such as polypyrrole, poly(N-substitutedpyrrole), poly(3-substituted pyrrole), or poly(3, or 4-disubstitutedpyrrole; polythiophenes such as polythiophene, poly(3-substitutedthiophene), poly(3,4-disubstituted thiophene), or polybenzothiophene;polyisothionaphthenes such as polyisothianaphthene; polythienylenevinylenes such as polythienylene vinylene; poly(p-phenylene vinylene)ssuch as poly(p-phenylene vinylene); polyanilines such as polyaniline,poly(N-substituted aniline), poly(3-substituted aniline), orpoly(2,3-disubstituted aniline); polycetylenes such as polyacetylene;polydiacetylenes such as polydiacetylene; polyazulenes such aspolyazulene; polypylenes such as polypylene; polycarbazoles such aspolycarbazole or poly(N-substituted carbazole), polyselenophenes such aspolyselenophene; polyfurans such as polyfuran or polybenzofuran;poly(p-phenylene)s such as poly(phenylene); polyindoles such aspolyindole; polypyridazines such as polypyridazine; polyacens such asnaphthacene, pentacene, hexacene, heptacene, dibenzopentacene,tetrabenzopentacene, pyrene, dibenzopyrene, chrysene, perylene,coronene, terylene, ovalene, quoterylene, or circumanthrathene;derivatives (triphenodioxazine, triphenodithiazine, andhexacene-6,15-quinone) in which some of the carbon atoms of polyacenesare substituted with atoms such as N, S, or O, or functional groups suchas a carboxyl group; polymers such as polyvinyl carbazole, polyphenylenesulfide, or polyvinylene sulfide; and polycyclic condensation productsdescribed in JP-A No. 11-195790. Further, preferably employed compoundsinclude oligomers such as α-sexithiophene-α,ω-dihexyl-α-sexithiophene,α,ω-dihexyl-α-quikethiophene, andα,ω-bis(3-butoxypropyl)-α-sexithiophene, which are thiophene hexamershaving the same repeat units as the above polymers, as well asstyrylbenzene derivatives.

Among these π conjugated oligomers and π conjugated polymers, preferredis at least one of:

the oligomers having repeat numbers of 4 to 19 or the polymers havingrepeat numbers of 20 or more; and

the oligomers or the polymers having a repeat unit of thiophene,vinylene, thienylene vinylene, phenylene vinylene, p-phenylene orsubstituent compounds thereof. It is also preferable that two or more ofthe above repeat units are contained in the oligomers having repeatnumbers of 4 to 19 or in the polymers having repeat numbers of 20 ormore. Specifically, oligomers or polymers containing thiophene orsubstituted thiophen are preferably used.

Specific example include polystyrene sulfonic acid complexes (PEDOT/PSScomplexes) (Baytron B, available from Bayer Corp.) of poly(ethylenedioxythiophene).

Preferable conductive polymers employed in the present invention includethe above mentioned π conjugated oligomers or π conjugated polymersbeing subjected to a doping treatment.

Preferred as dopants employed for the above doping treatment are aniondopants (p type dope), in view of the stability. The electricalconductivity of the conductive polymer is preferably 0.01 S/cm or more,and more preferably 1 S/cm or more.

Doping means that electron accepting molecules (acceptors) or electrondonating molecules (donors) are introduced into the aforesaid oligomersor polymers as a dopant. Employed as dopants in the present inventioninclude either acceptors or donors. Listed as such acceptors includehalogen compounds such as Cl₂, Br₂, I₂, ICl, ICl₃, IBr, IF; Lewis acidssuch as PF₅, AsF₅, SbF₅, BF₃, BCl₃, BBr₃, or SO₃; protonic acids such asHF, HCl, HNO₃, H₂SO₄, HClO₄, FSO₃H, ClSO₃H, or CF₃SO₃H; organic acidssuch as acetic acid, formic acid, or amino acids; transition metalcompounds such as FeCl₃, FeOCl, TiCl₄, ZrCl₄, HfCl₄, NbF₅, NbCl₅, TaCl₃,MoCl₃, WF₅, WCl₆, UF₆, LnCl₃ (Ln represents lantanoids such as La, Ce,Nd, or Pr and Y); and electrolyte anions such as Cl⁻, Br⁻, I⁻, ClO₄ ⁻,PF₆ ⁻, ASF₅ ⁻, SbF₆ ⁻, BF₄ ⁻, or a sulfonic acid anion. Listed as donorsinclude alkaline metals such as Li, Na, K, Rb, or Cs; alkaline earthmetals such as Ca, Sr, and Ba; rare earth metals such as Y, La, Ce, Pr,Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, or Yb; and other donors such as anammonium ion, R₄P⁺, R₄As⁺, R₃S⁺, or acetylcholine. Any conventionaldoping methods for these dopants may be utilized without any limitation.For example, it is possible to employ either a method in which a thinoligomer or polymer film is previously prepared and dopants are laterintroduced, or a method in which dopants are introduced during formationof the thin film of organic semiconductors. Listed as doping methods inthe former methods include:

a gas phase doping method in which gaseous dopants are employed;

a liquid phase doping method in which doping is performed in such amanner that liquid dopants are brought into contact with the aforesaidthin film; and

a solid phase doping method in which solid state dopants are broughtinto contact with the aforesaid thin film, followed by the diffusion ofthe dopants. In the liquid phase doping, it is possible to control thedoping efficiency by electrolysis. Also, in the liquid phase doping, asolution or a dispersed liquid containing a mixture of an organicsemiconductor compound and a dopant, or a mixture of an organicsemiconductor compound and a complex containing the dopant may be coatedthen dried. When a vacuum deposition method is employed, it is possibleto introduce dopants via deposition of organic semiconductor compoundstogether with dopants. On the other hand, when a thin film is preparedemploying a sputtering method, it is possible to introduce dopants intoa thin film, employing sputtering using two targets, namely, targets ofan organic semiconductor compound and of a dopant. Further, employed asother methods include chemical doping such as electrochemical doping andphoto-induced doping, and physical doping such as ion injection which isdescribed, for example, in Kogyo Zairyo (Industrial Materials) Volume34, No. 4, page 55. 1986.

It is preferable that the circuit patterns of the electrical circuit ofthe present invention are prepared by impregnating conductive polymersinto the aforesaid receptive layer, employing an ink-jet method, wherebyit is possible to more simply produce detailed electrical circuits.

The electrical circuit of the present invention is preferably formed byforming a circuit pattern by impregnating a conductive polymer in thereceptive layer by a ink-jet method. This method enables formation of anelectrical circuit having a fine pattern in a simple process. Further,in the present invention, it is preferable to form a circuit pattern insuch a manner that the impregnated amount of conductive polymer iscontrolled by controlling the amount of ejected conductive polymer perunit area employing an ink-jet method. The impregnated amount, asdescribed herein, refers to the impregnation distance of conductivepolymers in the receptive layer in the thickness direction. Since theelectrical circuit of the present invention is formed by impregnating aconductive polymer into the receptive layer, in a portion where theconductive polymer layer is intended to be electrically connected withterminal 4 in the electrical circuit described in FIG. 1, the ejectedamount of the conductive polymer solution per unit area may be increasedso as to increase the impregnated amount of conductive polymers in thatportion, resulting in forming an connection between the conductivepolymer layer and terminal 4. Alternatively, in a portion where theconductive polymer layer is intended not to connect with terminal 4, theejected amount of the conductive polymer solution per unit area may bedecreased so as to decrease the impregnated amount of conductivepolymers in that portion, resulting in forming no connection between theconductive polymer layer and terminal 4. With using this method, manyvariations may be introduced in circuit patter 3, whereby it becomespossible to form a variety of circuit patterns 3.

In the present invention, for impregnating the aforementioned conductivepolymer into the receptive layer, it is preferable to use a solution ordispersed liquid containing a conductive polymer. As solvents ordispersant, water or any arbitrary organic solvents may be used.However, in view of affinity with the receptive layer, which will bedescribed below, it is preferable that 30% or more of water iscontained. When an organic solvent is used, a water-soluble solvent ispreferable.

Listed as water-soluble organic solvents usable in the present inventioninclude, for example: alcohols (e.g., methanol, ethanol, propanol,isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol,pentanol, hexanol, cyclohexanol, and benzyl alcohol); polyhydricalcohols (e.g., ethylene glycol, diethylene glycol, triethylene glycol,polyethylene glycol, propylene glycol, dipropylene glycol, polypropyleneglycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol,and thioglycol); polyhydric alcohol ethers (e.g., ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether, ethylene glycolmonobutyl ether, diethylene glycol monomethyl ether, diethylene glycolmonomethyl ether, diethylene glycol monobutyl ether, propylene glycolmonomethyl ether, propylene glycol monobutyl ether, ethylene glycolmonomethyl ether acetate, triethylene glycol monomethyl ether,triethylene glycol monomethyl ether, triethylene glycol monobutyl ether,ethylene glycol monophenyl ether, and propylene glycol monophenylether); amines (e.g., ethanolamine, diethanolamine, triethanolamine,N-methyldiethanolamine, N-ethyldiethanolamine, morpholine,N-ethylmorpholine, ethylenediamine, diethylenediamine,triethylenetetramine, tetraethylenepentamine, polyethyleneimine,pentamethyldiethylenetriamine, and tetramethylpropylenediamine; amides(e.g., formamide, N,N-dimethylformamide, and N,N-dimethylacetamide);heterocycles (e.g., 2-pyrrolidone, N-methyl-2-pyrrolidone,cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone);sulfoxides (e.g., dimethylsulfoxide); sulfones (e.g., sulfolane); otherssuch as urea, acetonitrile, and acetone. Listed as preferredwater-soluble organic solvents are polyhydric alcohols. Further, it isspecifically preferable that polyhydric alcohols and polyhydric alcoholethers are used in combination.

Water-soluble organic solvents may be employed alone or in combinationsof a plurality of the solvents. The added amount of a water-solublesolvent is commonly 5-70 percent by weight based on the total weight,but is preferably 10-30 percent by weight.

In addition, it is possible to add a variety of surfactants.Specifically, when a conductive polymer solution or dispersed liquid isejected by an ink-jet method, the resulting surface tension ispreferably controlled in the range of 30×10⁻³ to 40×10⁻³ N/m by adding asurfactant. When an anion doped conductive polymer is employed, anonionic surfactant is suitably used. When an ink-jet method isemployed, the viscosity of the solution or dispersed liquid containingthe conductive polymer is preferably controlled within 1 to 15 cp, byadjusting the concentration of the conductive polymer.

As an ink-jet head of an ink-jet printer, any of conventionally usedpiezo head or thermal head is appropriately employed. Further, either anon-demand system or a continuous system may be employed.

In the present invention, the receptive layer is designated as a layerin which the conductive polymer is absorbed and fixed by impregnatingthe conductive polymer in it.

The receptive layer may be classified mainly into a swelling type and aporous type. The swelling type layer is prepared by coating acomposition containing water-soluble binders, for example, gelatin,water-soluble polymers other than gelatin, latex, and polyurethane.These binders may be used alone or in combination. Gelatin and otherwater-soluble polymers are preferably used in the receptive layerbecause of the large absorbing capacity and the high drying rate.

Any gelatin may be employed as long as the gelatin is prepared employinganimal collagen as a raw material. However, more preferred is gelatinprepared employing pigskin collagen, cattle hide collagen, or cattlebone collagen as a raw material. The kinds of gelatin are notspecifically limited, and include lime-processed gelatin, acid-processedgelatin and gelatin derivatives (for example, disclosed in ExaminedJapanese Patent Publication Nos. 38-4854, 39-5514, 40-12237, and42-26345; U.S. Pat. Nos. 2,525,753, 2,594,293, 2,614,928, 2,763,639,3,118,766, 3,132,945, 3,186,846, and 3,312,553; and British Patent Nos.861,414 and 103,189), and they may be used alone or in combination. Useof acid-processed gelatin is advantageous in order to increase waterresistance.

Listed as water-soluble polymers preferably employed in the swellingtype receptive layer other than gelatin include, for example, vinylformals such as polyvinyl alcohols, polyvinylpyrrolidones,polyvinylpyridinium halide, or various. modified polyvinyl alcohols andderivatives thereof (refer to JP-A Nos. 60-145879, 60-220750, 61-143177,61-235182, 61-235183, 61-237681, and 61-261089); polymers containing anacryl group (disclosed in JP-A Nos. 60-168651 and 62-9988) such aspolyacryl amide, polydimethylacryl amide, polydimethylaminoacrylate,sodium polyacrylate, acrylic acid-methacrylic acid copolymers, sodiumpolymethacrylate, acrylic acid-vinyl alcohol copolymer salts; naturalpolymers or derivatives thereof (disclosed in JP-A Nos. 59-174382,60-262685, 61-143177, 61-181679, 61-193879, and 61-287782) such asstarch, oxidized starch, carboxyl starch, dialdehyde starch, cationizedstarch, dextrin, sodium alginate, gum Arabic, casein, pullulan, dextran,methyl cellulose, ethyl cellulose, carboxymethyl cellulose, orhydroxypropyl cellulose; and synthetic polymers (disclosed in JP-A Nos.61-32787, 61-237680, and 61-277483) such as polyethylene glycol,polypropylene glycol, polyvinyl ether, polyglycerin, alkyl maleate-vinylether copolymers, maleic acid -N-vinyl-pyrrole copolymers,styrene-maleic anhydride copolymer. Of these polymers, preferred arepolyvinyl pyrrolidone, polyvinyl alcohols, or polyalkylene oxides.

Preferred as porous receptive layer are those which are prepared in sucha manner that micro particles and water-soluble binders are mixed andthen coated.

Micro particles usable in the present invention include inorganic andorganic particles. However, specifically preferred are inorganicparticles since they are easily obtained. Examples of such inorganicparticles include white inorganic pigments such as precipitated calciumcarbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay,talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide,zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalsite, aluminumsilicate, diatomaceous earth, calcium silicate, magnesium silicate,synthetic non-crystalline silica, colloidal silica, alumina, colloidalalumina, pseudo boehmite, aluminum hydroxide, lithopone, zeolite, ormagnesium hydroxide. It is possible to use the above inorganic particlesin the form of primary particles without any modification or in thestate in which secondary coagulated particles are formed.

In the present invention, preferred as inorganic particles are alumina,pseudo boehmite, and colloidal silica, as well as minute silicaparticles synthesized by a vapor deposition method which are alsoreferred to as fumed silica particles. Of these, most preferred areminute silica particles synthesized by a vapor deposition method (alsoreferred to as fumed silica particles). Also, the surface of the fumedsilica particle may be modified by Al. The content of Al in the Almodified fumed silica particles is preferably 0.05 to 5 percent byweight based on the weight of silica.

It is possible to use any diameter of the above micro inorganicparticles. However, the average particle diameter is preferably not morethan 1 μm, but specifically preferably not more than 0.1 μm. Even thoughthe lower limit of the particle diameter is not specified, it ispreferably not less than 0.003 μm, but is more preferably not less than0.005 μm, in order to efficiently produce the particles.

The average diameter of the above inorganic particles is determined asfollows. The section and surface of a porous layer is observed throughan electron microscope, and the diameter of randomly selected 100particles is determined. Subsequently, the simple average value (thenumber average value) is obtained. Herein, “the particle diameter”refers to the diameter of a circle having the same area as theprojective area of the particle.

The above micro particles may exist in the porous layer as primaryparticles, secondary particles, or higher order coagulated particles.The average particle diameter, as described above, refers to thediameter of a particle which is individually formed in the porous layerunder the observation of an electron microscope.

The amount of the above micro particles in an aqueous coatingcomposition is 5 to 40 percent by weight, but is more preferably 7 to 30percent.

Hydrophilic binders incorporated in a porous receptive layer are notparticularly limited, and it is possible to use conventional hydrophilicbinders known in the art. For example, employed may be gelatin,polyvinylpyrrolidone, polyethylene oxide, polyacrylamide, and polyvinylalcohol. Of these, polyvinyl alcohol is specifically preferable.

Polyvinyl alcohol is a polymer which exhibits interaction with inorganicparticles, resulting in strong holding force for inorganic particles,and also exhibits hygroscopicity of relatively small humiditydependence. In addition to the common polyvinyl alcohol prepared byhydrolyzing polyvinyl acetate, polyvinyl alcohols preferably employed inthe present invention include a modified polyvinyl alcohols, forexample, a cation-modified polyvinyl alcohol of which end iscation-modified or an anion-modified polyvinyl alcohol having an anionicgroup.

The average polymerization degree of polyvinyl alcohol prepared byhydrolyzing vinyl acetate is preferably not less than 300, and is morepreferably 1,000 to 5,000. The saponification ratio is preferably 70 to100 percent, and is more preferably 80 to 99.5 percent.

Examples of cation-modified polyvinyl alcohol include those having aprimary, secondary or tertiary amino group, or a quaternary ammoniumgroup in the main chain or the side chain of the above polyvinyl alcoholwhich are, for example, disclosed in JP-A No. 61-10483. Such polyvinylalcohol is prepared by saponifying a copolymer of vinyl acetate and anethylenically unsaturated monomer having a cationic group.

Listed as ethylenically unsaturated monomers having a cationic groupinclude, for example, trimethyl-(2-acrylamido-2,2-dimethylethyl)ammoniumchloride, trimethyl-(3-acrylamido-3,3-dimethylpropyl)ammonium chloride,N-vinylimidazole, N-vinyl-2-methylimidazole,N-(3-dimethylaminopropyl)methacrylamide, hydroxyethyltrimethylammoniumchloride, trimethyl-(3-methsacylamidopropyl)ammonium chloride, andN-(1,1-dimethyl-3-dimethylaminopropyl)acrylamide.

The ratio of monomers having a cation-modified group of cation-modifiedpolyvinyl alcohol is commonly 0.1 to 10 mol percent based on vinylacetate, but is preferably 0.2 to 5 mol percent.

Listed as anion-modified polyvinyl alcohols include, for example,polyvinyl alcohol having an anionic group disclosed in JP-A No.1-206088, a copolymer of polyvinyl alcohol and a vinyl compound having awater-soluble group disclosed in JP-A Nos. 61-237681 and 63-307979, andmodified polyvinyl alcohol having a water-soluble group disclosed inJP-A No. 7-285265.

Further listed as nonion-modified polyvinyl alcohols include, forexample, a polyvinyl alcohol derivative in which a polyalkylene oxidegroup is added to a part of vinyl alcohol, disclosed in JP-A No. 7-9758,and a block copolymer of a vinyl compound having a hydrophobic group andvinyl alcohol, disclosed in JP-A No. 8-25795.

Polyvinyl alcohols may be employed in combinations of at least two typesbeing different in the degree of polymerization or in kinds ofmodifications. Specifically, when polyvinyl alcohol having a degree ofpolymerization of 2,000 or more is employed, it is preferable thatpolyvinyl alcohol having a degree of polymerization of 1,000 or less isinitially mixed with dispersed inorganic particle, the amount of thepolyvinyl alcohol being 0.05 to 10 percent by weight, but preferably0.1-5 percent by weight, based on the weight of the inorganic particles.The mixture was, then, further mixed with a polyvinyl alcohol having adegree of polymerization of 2,000 or more. In this way, a drasticincrease in viscosity is avoided.

The ratio of micro particles to hydrophilic binders in a porousreceptive layer is preferably between 2:1 and 20:1 by weight. When theweight ratio of micro particles is less than 2:1, the porosity of theporous layer decreases, whereby it becomes difficult to obtain asufficient pore volume, and in addition, excessively existinghydrophilic binders tends to swell during ink-jet printing, resulting insealing the pores and, further, resulting in an decrease in theabsorption rate of a conductive polymer. On the other hand, when theweight ratio of micro particles is more than 20:1, cracking tends tooccur, especially when a relatively thick porous layer is formed. Theratio of micro particles to a hydrophilic binder in a prous receptivelayer is preferably between 2.5:1 and 12:1 by weight, but morepreferably between 3:1 and 10:1 by weight.

In the electrical circuit of the present invention, the receptive layeris preferably a porous layer. By employing the porous receptive layer,the impregnation rate of a solution or a dispersed liquid containing theconductive polymer is increased, whereby the patterning accuracy isenhanced. Further, compared to the swelling type receptive layer, theconductivity of the impregnated portion is larger. In addition,depending on the properties of a conductive polymer, it is possible toappropriately select micro particles and hydrophilic binders, whereby itis possible to easily control the degree of impregnation of theconductive polymer.

The thickness of the receptive layer is preferably in the range of 0.05to 50 μm, but more preferably in the range of 0.5 to 20 μm.

Since the electrical circuit of the present invention has a receptivelayer provided on the substrate, it exhibits higher durability and, as aresult, a process of annealing the electrical circuit at a hightemperature is not necessary. Accordingly, in addition to theconventionally employed substrate materials such as glass, a highmelting point resin, silicone, or a metal film, a variety of polymermaterials are usable as a substrate in the electrical circuit of thepresent invention. By using a variety of polymer materials, theelectrical circuit of the present invention has become possible to beapplied to a flexible print circuit or a flexible display.

Listed as usable polymers include, for example, polyesters such aspolyethylene terephthalate (PET) and polyethylene naphthalate (PEN),polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol,syndiotactic polystyrene, polyethylene, polypropylene, cellophane,polyether sulfone (PES), polyether imide, polyether ether ketone,polysulfone, polyphenylene sulfide, polyacrylate, polyimide, polyamide,polycarbonate (PC), norbonene resins, polymethyl pentene, fluoricresins, nylon, polymethyl methacrylate, acryl or polyarylates, celluloseesters such as cellulose triacetate (TAC), cellulose diacetatepropionate (CAP), cellulose acetate butyrate, cellulose acetatephthalate, cellulose nitrate, and derivatives thereof.

These polymer films may be subjected to surface treatment or surfacecoating known in the art. For example, formed as a gas barrier layerinclude: a film which is prepared by co-deposition of silicon oxide andaluminum oxide; a film of a mixture of metal oxides such as siliconoxide and aluminum oxide, which is prepared employing an atmosphericpressure plasma method; and a multilayer composite film thereof. Acomposite film may be prepared by laminating a film formed by depositionof a thin layer of metal such as aluminum by an evaporation method. Afilm may also be mixed with micro particles of a metal oxide. As notedabove, by employing a plastic film as the substrate, it is possible todecrease the weight of the circuit compared to the case when a glasssubstrate is used. Moreover, portability is enhanced as well asdurability against impact is increased.

The term, “a circuit pattern formed with conductive materials” refers toa pattern of an electrode or an electric wiring formed by usingconductive materials. However, the present invention is not limitedthereto. A member existing in the electrical circuit and the memberbeing capable of forming by using the conductive polymer may also beincluded in the circuit pattern.

The thin film transistor of the present invention will now be explained.

In FIG. 3( a), shown is a sectional view of one example of the thin filmtransistor of the present invention, while in FIG. 3( b), shown is aplan view of one example of the thin film transistor of the presentinvention.

In FIG. 3, numeral 1 is a substrate, while 2 is a receptive layer.Further, 3 a is a source electrode, and 3 b is a drain electrode, while4 a is a semiconductor, 4 b is a source bus line, and 4 c is a pixelelectrode. It is possible to use the pixel electrode as an inputelectrode of sensors, as well as an address electrode or an outputelectrode of displays. Numeral 5 is a gate electrode, 6 is a gateinsulating layer which insulates gate electrode 5 from semiconductorlayer 4 a, source bus line 4 b, and display electrode 4 c. As substrate1 and receptive layer 2, the aforementioned substrate and receptivelayer are applicable.

In the thin film transistor of the present invention, circuit patternsof source electrode 3 a and drain electrode 3 b are formed byimpregnating conductive polymers into receptive layer 2. The conductivepolymers are not accumulated on the surface of receptive layer 2 butimpregnated into the interior of the receptive layer and fixed. As aresult, spread of the conductive polymers is limited, whereby it ispossible to form fine and complicated source electrode 3 a as well asdrain electrode 3 b.

Further, even though the surface of receptive layer 2 has damage such asscratches, in the thin film transistor of the present invention, sourceelectrode 3 a and drain electrode 3 b are impregnated in the receptivelayer, whereby damage for the circuit is only limited. As a result, noprotective layer on the surface of the receptive layer is needed, whichhas conventionally been necessary. In addition, since durability isenhanced by providing receptive layer 2, no heat treatment such asannealing is needed. Consequently, a thin film transistor ismanufactured in a short and simple process.

In the thin film transistor of the present invention, source electrode 3a and drain electrode 3 b are formed by impregnating a conductivepolymer into receptive layer 2. These electrode can be formed by usingthe above mentioned conductive polymers.

The thin film transistor of the present invention will now be detailed.

It is preferable that in the thin film transistor of the presentinvention, the source electrode and the drain electrode are formed byimpregnating a conductive polymer into the above receptive layer,employing an ink-jet method. As a result, it becomes possible to simplyand accurately produce thin film transistors.

The thickness of the source electrode as well as the drain electrode isnot practically limited as long as both are impregnated into the abovereceptive layer. The thickness is preferably 0.05 to 50 μm, but is morepreferably 0.5 to 20 μm.

Moreover, in the thin film transistor of the present invention, it ispreferable that the source electrode as well as the drain electrode isformed by controlling the impregnated amount of conductive polymerswhile controlling the ejection amount of the conductive polymer solutionper unit area of the receptive layer, employing an ink-jet method. As aresult, it becomes possible to form a variety of source electrodes aswell as drain electrodes.

In the thin film transistor of the present invention, it is preferablethat the receptive layer is a porous layer. By employing the porousreceptive layer, it is possible to suitably select micro particles aswell as hydrophilic binders according to the properties of theconductive polymers, whereby it is possible to easily control the degreeof impregnation of conductive polymers.

As the substrate of the thin film transistor of the present invention,various polymer materials can be used because no annealing process isneeded due to enhanced durability as the result of providing thereceptive layer. It becomes possible to apply substrates to electricalcircuits which may be used, for example, for flexible print circuits andflexible displays. Above mentioned polymers are preferably used for thesubstrate.

Electrode materials employed for gate electrodes, source bus lines, andpixel electrodes of the thin film transistor of the present inventionare not specifically limited as long as they are conductive materials.Employed are platinum, gold, silver, nickel, chromium, iron, tin,antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium,aluminum, ruthenium, germanium, molybdenum, tungsten, tinoxide.antimony, indium oxide.tin (ITO), fluorine-doped zinc oxide, zinc,carbon, graphite, glassy carbon, silver paste, carbon paste, lithium,beryllium, sodium, magnesium, potassium, calcium, scandium, titanium,manganese, zirconium, gallium, niobium, sodium-potassium alloy,magnesium/copper mixtures, magnesium/silver mixtures, magnesium/aluminummixtures, magnesium/indium mixtures, aluminum/aluminum oxide mixtures,and lithium/aluminum mixtures. Of these, specifically preferable areplatinum, gold, silver, copper, aluminum, indium, ITO, and carbon.

Examples of methods for forming a gate electrode, a source bus line, anda display electrode include:

preparing a conductive thin film employing a evaporation method or asputtering method followed by patterning the film using aphotolithographic method or a lift-off method to form the electrodes;

forming a resist pattern on a metal film, for example, an aluminum filmor a copper film employing a thermal transfer method or an ink-jetmethod, followed by etching;

directly forming a pattern of a solution of conductive polymer, adispersed liquid containing conductive polymer or conductive microparticles, employing an ink-jet method;

forming a pattern of a metal layer employing lithography or laserablation; and

printing a pattern of a conductive ink containing such as a conductivepolymer, conductive micro particles, or a conductive paste employing aprinting method, for example, relief printing, intaglio printing,lithography, or screen printing.

A variety of insulator films are applicable for a gate insulation layerof the thin film transistor of the present invention. Specifically,inorganic oxide films exhibiting a high dielectric constant arepreferable. Listed as inorganic oxides include silicon oxide, aluminumoxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, bariumstrontium titanate, barium zirconate titanate, lead zirconate titanate,lead lanthanum titanate, strontium titanate, barium titanate, bariummagnesium fluoride, bismuth titanate, strontium bismuth titanate,strontium bismuth tantalate, bismuth tantalate niobate, and yttriumtrioxide. Of these, preferred are silicon oxide, aluminum oxide,tantalum oxide, and titanium oxide. In addition, inorganic nitrides andnitride-oxides such as silicon nitride as well as aluminum nitride arealso preferable.

Listed as methods for forming the above films include: dry processmethods such as a vacuum evaporation method, a molecular beam epitaxialdeposition method, an ion cluster beam method, a low energy ion beammethod, an ion plating method, a CVD method, a sputtering method, or anatmospheric pressure plasma method; as well as wet process methods suchas coating methods including a spray coating method, a spin coatingmethod, a blade coating method, a dip coasting method, a casting method,a roller coating method, a bar coating method, and a die coating method,and methods forming patterns such as a printing method or an ink-jetmethod. These methods are employed depending on materials.

The wet processes include, for example:

a method to apply and dry a dispersed liquid of micro particles of aninorganic oxide in any kind of organic solvent or water containingsolvent, together with a dispersing agent, for example, a surfactant;and

a method to apply and dry a solution of a precursor of an inorganicoxide, for example, an alcoxide, so-called a sol-gel method.

Of these, preferable is an atmospheric pressure plasma method.

A method for forming a gate insulation layer, employing a plasma filmingprocess under an atmospheric pressure, refers to the method in which areactive gas is subjected to plasma excitation while discharged under anatmospheric pressure or a pressure near the atmospheric pressure, and athin film is formed on a substrate. The above method is described, forexample, in JP-A Nos. 11-61406, 11-133205, 2000-121804, 2000-147209, and2000-185362. This method makes it possible to form a highly functionalthin film at higher productivity.

Further, materials to form an organic compound film include, forexample: polyimide, polyamide, polyester, polyacrylate, a photocurableresin based on photo-radical polymerization, a photocurable resin basedon photo-cation polymerization, polyacrylonitrile,polymethacrylonitrile, a copolymer containing acrylonitrile ormethacrylonitrile component, polyvinylphenol, polyvinyl alcohol, anovolac resin, and cyanoethylpullulan.

Preferably employed as a method for forming organic compound films isthe aforesaid wet process method.

An inorganic oxide film may be employed together with an organic oxidefilm via lamination. The thinness of these insulation films is commonly50 nm to 3 μm, but is preferably 100 nm to −1 μm.

Employed as materials used in a semiconductor layer of the thin filmtransistor of the present invention include semiconductor materials suchas amorphous silicone and poloysilicone, as well as organicsemiconductor materials known in the art.

Listed as organic semiconductor materials include:

the above-mentioned π conjugated polymers and oligomers;

acenes such as pentacene;

metal phthalocyanines such as copper phthalocyanine, andfluorine-substituted copper phthalocyanine;

condensed ring tetracarboxylic acid diimides including naphthalenetetracarboxylic acid diimides such asnaphthalene-1,4,5,8-tetracarboxylic acid diimide,N,N′-bis(4-trifluoromethylbenzyl)naphthalene-1,4,5,8-tetracarboxylicacid diimide, N,N′-bis(1H,1H-perfluorooctyl),N,N′-bis(1H,1H-perfluorobutyl), orN′-dioctylnaphthalene-1,4,5,8-tetracarbocylic acid diimide derivatives,naphthalene-2,3,6,7-tetracarboxylic acid diimide and anthracenetetracarboxylic acid diimides such as anthracene-2,3,6,7-tetracarboxylicacid;

dyes such as merocyanine dyes or hemicyanine dyes; and

organic molecular complexes such as a tetrathiafluvalene(TTF)-tetracyanoquinodimethane (TCNQ) complex, abisethylenetetrathiafluvalene (BEDTTTE)-perchloric acid complex, aBEDTTTF-iodine complex, or a TCNQ-iodine complex. In addition, employedmay be σ conjugated polymers such as polysilane or polygermane,organic-inorganic composite materials described in JP-A No. 2000-260999,fullerenes such as C60 or C70, and carbon nanotubes such as SWNT.

When a polymer is employed as a substrate, it is preferable to use anorganic semiconductor material which can be treated at a lowertemperature.

In the present invention, a semiconductor layer may be subjected to theaforesaid doping treatment.

Listed as methods for forming the thin film of these semiconductorsinclude: a vacuum evaporation method, a molecular beam epitaxialdeposition method, an ion cluster beam method, a low energy ion beammethod, an ion plating method, a CVD method, a sputtering method, aplasma polymerization method, an electrolytic polymerization method, achemical polymerization method, a spray coating method, a spin coatingmethod, a blade coating method, a dip coasting method, a casting method,a roller coating method, a bar coating method, a die coating method, anda LB method, which may be chosen according to the materials. Of these,the coating methods by which a thin film is precisely and easilyobtained, for example, a spin coating method, a blade coating method, adip coating method, a roller coating method, a bar coating method and adie coating method, are preferably used, also, in view of theproductivity. The thickness of the thin film of these semiconductors isnot specifically limited. However, in many cases, the characteristics ofthe obtained transistor largely depend on the thickness of the activelayer of the organic semiconductors, and the preferable thicknessdiffers depending on the organic semiconductors. The thickness iscommonly not more than 1 μm, preferably 10 to 300 nm, but morepreferably 20 to 100 nm.

Further, the total film thickness of the thin film transistor of thepresent invention is not specifically limited, and is preferably in therange of 0.1 to 50 μm, but is more preferably in the range of 0.5 to 10μm.

EXAMPLES

The present invention will be explained using the following examples,however, the present invention is not limited thereto. FIG. 4 will beused for the explanation of the production process of the following thinfilm transistors.

Example 1

On substrate 1 which was a 200 μm thick PES film, a 200 nm thickaluminum film was deposited employing a sputtering method. Subsequently,the aluminum film was patterned by employing photolithography to formgate electrode 5 (refer to FIG. 4( a)). Further, a 200 nm thick siliconoxide film was formed under the following conditions, employing anatmospheric pressure plasma method to form gate insulator layer 6 (referto FIG. 4( b)). The film temperature during the formation was maintainedat 180° C.

(Used Gas)

Inert gas: helium 98.25 percent by volume

Reactive gas: oxygen gas 1.5 percent by volume

Reactive gas: tetraethoxysilane vapor (bubbled employing helium gas)0.25 percent by volume

(Discharge Condition)

Discharge power: 10 W/cm²

Further, water repellent treatment was performed on a silicon oxidefilm, employing a plasma method.

Further, on gate insulation layer 6, pentacene, as semiconductor 4 a,was formed with a thickness of 50 nm through a mask, utilizing thermalevaporation. Further, source bus line 4 b and pixel electrode 4 c wereformed with a thickness of 1 μm, employing commercially available silverpaste via a screen printing method (refer to FIG. 4( c))

Coating liquid composition 1, as described below, was applied so thatsource bus line 4 b, semiconductor layer 4 a, and pixel electrode 4 cwere covered, employing a wire bar and subsequently dried to form areceptive layer of a thickness of 5 μm (refer to FIG. 4( d)). Thereceptive layer may be applied over the entire surface. However, anycoating may be acceptable as long as the coating simultaneously coverssource bus line 4 b and pixel electrode 4 c.

(Coating Liquid Composition 1)

After 0.6 kg of AEROSIL 300 (at a primary particle diameter of 7 nm)produced by Nippon Aerosil Co., Ltd. was suction-dispersed into 3 kg ofcolloidal silica (at a primary particle diameter of 10-20 nm, 20 percentaqueous dispersion, produced by Nissan Chemical Industries, Ltd.),AEROSIL 300 being fumed silica particles, pure water was added toprepare 7 L of the dispersed liquid. Further, 0.7 L of an aqueoussolution containing 27 g of boric acid and 23 g of borax, and 1 g adefoamer (SN381, produced by Sannopco Co.) were added. The resultingmixture was dispersed twice employing a high pressure homogenizer at apressure of 2.45×I0⁷ Pa, whereby an aqueous silica-dispersed liquid wasprepared. While stirring at 40° C., 1 L of 5 percent aqueous polyvinylalcohol solution was added to 1 L of the resulting aqueoussilica-dispersed liquid, whereby a receptive layer coating liquidcomposition was prepared.

Subsequently, an aqueous PEDOT/PSS complex dispersion (produced by BayerCorp.) as a conductive polymer liquid composition was diluted to twiceby water and a nonionic surface active agent (polyoxyethylene alkylether) was added in an amount of 0.05 percent by weight.

Thereafter, source electrode 3 a and drain electrode 3 b were formed insuch a manner that the resulting mixture was ejected employing anink-jet head of a piezo system, impregnated into receptive layer 2 andthen dried, whereby a thin layer transistor was prepared (refer to FIG.4( e)). The effective channel length and channel width were 20 μm and200 μm, respectively.

The resulting thin film transistor worked well as a p channelenhancement type FET (Field Effect Transistor), and the mobility ofcarriers in the saturated region was 0.4 cm2/Vs.

Example 2

A thin film transistor was prepared in the same manner as Example 1,except that a 5 μm thick polyvinyl alcohol (PVA) layer was formed as areceptive layer by employing an aqueous PVA solution. The mobility ofcarriers in the saturated region was 0.08 cm²/Vs.

Comparative Example

A thin film transistor was prepared in the same manner as Example 1,except that the receptive layer was not formed. The resulting transistordid not work because a short circuit was formed between source electrode3 a and drain electrode 3 b.

As described above, when a thin film transistor is produced by formingcircuit patterns of source electrode 3 a and drain electrode 3 b byimpregnating a conductive polymer into a receptive layer, the conductivepolymer is not accumulated on the surface of the receptive layer but isimpregnated and fixed in the receptive layer. Consequently, the spreadof the conductive polymer is suppressed and fine and complex patterns ofsource electrode 3 and drain electrode 3 b are successfully formed.Further, even when the surface of receptive layer 2 is damaged due toscratching, the damage to the electrical circuit is only limited, sincesource electrode 3 a and drain electrode 3 b are impregnated in thereceptive layer. As a result, since it is unnecessary to newly provide aprotective layer on the surface of the receptive layer, contrary to theconventional thin film transistors, it is possible to quickly and simplyproduce a thin film transistor.

EFFECTS OF THE INVENTION

According to the present invention, it is possible to provide: anelectrical circuit and a thin film transistor capable of being simplyand quickly formed without necessitating processes such as a thermaltreatment; a method for producing an electrical circuit which enablessimply and quickly forming an electrical circuit having a fine andcomplex circuit pattern; and a method for producing a thin filmtransistor.

1. A method for manufacturing an electrical circuit comprising a step offorming at least a part of the electrical circuit by impregnating aconductive polymer solution in a solvent or a conductive polymerdispersed liquid in a dispersant, in a receptive layer formed on asubstrate, the conductive polymer exhibiting p-type conduction or n-typeconduction, wherein the receptive layer contains inorganic particles andthe receptive layer is porous.
 2. The method for manufacturing the partof the electrical circuit of claim 1, comprising the steps of: afterimpregnating the solution or the dispersed liquid containing theconductive polymer in the receptive layer, forming the part of theelectrical circuit by evaporating the solvent of the solution containingthe conductive polymer or the dispersant of the dispersed liquidcontaining the conductive polymer.
 3. The method for manufacturing theelectrical circuit of claim 2, wherein the solvent of the solutioncontaining the conductive polymer or the dispersant of the dispersedliquid containing the conductive polymer contains 30% or more of water.4. The method for manufacturing the electrical circuit of claim 2,wherein the solvent of the solution containing the conductive polymer orthe dispersant of the dispersed liquid containing the conductive polymercontains 5 to 70% by weight of a water soluble organic solvent.
 5. Themethod for manufacturing the electrical circuit of claim 4, wherein thesolvent of the solution containing the conductive polymer or thedispersant of the dispersed liquid containing the conductive polymercontains 10 to 30% by weight of a water soluble organic solvent.
 6. Themethod for manufacturing the electrical circuit of claim 2, wherein thesolution or the dispersed liquid containing the conductive polymer has0.001 to 1% by weight of a surfactant.
 7. The method for manufacturingthe electrical circuit of claim 6, wherein the surfactant is a non-ionicsurfactant.
 8. The method for manufacturing the electrical circuit ofclaim 2, wherein the solution or the dispersed liquid containing theconductive polymer is impregnated in the receptive layer by ejecting thesolution or the dispersed liquid containing the conductive polymer ontothe receptive layer by a ink-jet printing method.
 9. The method formanufacturing the electrical circuit of claim 8, wherein an amount ofthe conductive polymer impregnated in the receptive layer is controlledby controlling an amount of the ejected solution or the dispersed liquidcontaining the conductive polymer per unit area.
 10. The method formanufacturing the electrical circuit of claim 1, wherein the part of theelectrical circuit is formed by ejecting the conductive polymer onto thereceptive layer by a ink-jet printing method so as to impregnate theejected conductive polymer in the receptive layer.
 11. The method formanufacturing the electrical circuit of claim 10, wherein an amount ofthe conductive polymer impregnated in the receptive layer is controlledby controlling an amount of the ejected conductive polymer per unitarea.
 12. The method for manufacturing the electrical circuit of claim1, wherein: the conductive polymer is an oligomer having a repeat numberof 4 to 19 or a polymer having a repeat number of 20 or more; and theconductive polymer has a repeat unit of thiophene, vinylene, thienylenevinylene, phenylene vinylene, p-phenylene or a substituent compoundthereof.
 13. The method for manufacturing the electrical circuit ofclaim 12, wherein the conductive polymer is an oligomer or a polymerhaving thiophene or substituted thiophene as a repeat unit.
 14. Themethod for manufacturing the electrical circuit of claim 12, wherein theoligomer or the polymer contains a dopant.
 15. The method formanufacturing the electrical circuit of claim 1, wherein an electricalconductivity of the conductive polymer is 0.01 S/cm or more.
 16. Themethod for manufacturing the electrical circuit of claim 15, wherein theelectrical conductivity of the conductive polymer is 1 S/cm or more. 17.The method for manufacturing the electrical circuit of claim 1, whereinthe inorganic particles are fumed silica particles.
 18. The method formanufacturing the electrical circuit of claim 1, wherein an averageparticle diameter of the inorganic particles is 0.003 to 0.2 μm.
 19. Themethod for manufacturing the electrical circuit of claim 18, wherein theaverage particle diameter of the inorganic particles is 0.005 to 0.1 μm.20. The method for manufacturing the electrical circuit of claim 1,wherein: the receptive layer further contains a hydrophilic binder; anda weight ratio of the inorganic particles to the hydrophilic binder isbetween 2:1 and 20:1.
 21. The method for manufacturing the electricalcircuit of claim 1, wherein the substrate is a polymer.
 22. A method formanufacturing an electrical circuit comprising a step of forming atleast a part of the electrical circuit by impregnating a conductivepolymer solution or a conductive polymer dispersed liquid in a receptivelayer formed on a substrate, the conductive polymer exhibiting p-typeconduction or n-type conduction, wherein the receptive layer is porous;and the receptive layer comprises at least particles selected from thegroup consisting of alumina particles, pseudo boehmite particles,colloidal silica particles and fumed silica particles.
 23. A method formanufacturing an electrical circuit comprising a step of forming atleast a part of the electrical circuit by impregnating a conductivepolymer solution or a conductive polymer dispersed liquid in a receptivelayer formed on a substrate, the conductive polymer exhibiting p-typeconduction or n-type conduction, wherein the receptive layer containsinorganic particles and a hydrophilic binder; and a weight ratio of theinorganic particles to the hydrophilic binder is between 2:1 and 20:1.